Distribution and vocal behavior of Atlantic
white-sided dolphins (Lagenorhynchus acutus)
in northern Norway
Ellyne Terese Hamran
BI309F MSc IN MARINE ECOLOGY
Faculty of Biosciences and Aquaculture
October 2014
0
Table of Contents
Foreword…………………………………………………………………………3
Abstract…………………………………………………………………………..4
Introduction……………………………………………………………………...5
Atlantic White-sided Dolphin Distribution and Biology…………………5
Social and Acoustic Behavior in Dolphins……………………………….8
Atlantic White-sided Dolphin and White-beaked Dolphin Distribution…10
Aim of Study……………………………………………………………..11
Methods………………………………………………………………………….13
Study Area and Survey Platform………………………………………....13
Sightings and Photo-ID…………………………………………………...14
Behavioral Sampling……………………………………………………..15
Acoustic Sampling
…………………………………………………….16
Analysis…………………………………………………………………...16
Results…………………………………………………………………………….19
Sightings and Photo-ID…………………………………………………...19
Behavioral Observations………………………………………………….23
Acoustic Behavior………………………………………………………..24
Whistles and Stereotyped Whistles………………………………………26
Hydrophone Recordings……………………………………………….....27
Sound Production and Activity…………………………………………...28
Sound Production and Depth……………………………………………..31
Group Affiliation…………………………………………………………32
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Discussion……………………………………………………………………..……..35
Sightings and Photo-ID………………………………………………...……..35
Distribution in Norway…………………………………………………...…..36
Foraging and Social Behavior…………………………………………….….38
Acoustic Behavior…………………………………………………….............39
Sound Production and Activity………………………………………………..41
Sound Production and Depth………………………………………………….43
Comparison of White-beaked Dolphins and Atlantic White-sided Dolphins…44
Conclusions…………………………………………………………………...45
Acknowledgements………………………………………………………………..…48
References………………………………………………………………………..…..49
Appendix………………………………………………………………………………55
Appendix 1: Photo-ID of Norwegian Atlantic White-sided Dolphins………....55
Appendix 2: Histogram frequency distributions of sounds produced………….67
Appendix 3: Boxplots of sounds produced and socializing per sighting date …69
Appendix 4: Boxplots of sounds produced and traveling per sighting date……70
Appendix 5: Boxplots of sounds produced and foraging per sighting date…….71
Appendix 6: Boxplots of sounds produced and milling per sighting date………72
2
Foreword
Journal style: Journal of Applied Ecology. Reports such as the Norwegian Marine Institute
and additional were referenced as reports with document numbers and referenced in the text
with author(s) and year.
Dolphin Naming: The usage of the common names of Atlantic White-sided Dolphins and
White-beaked Dolphins became confusing if detail to the second half of the name were
ignored hence the Latin names were more distinctive and preferred.
Maps: Maps were created in ArcGIS (desktop Advanced 10.2.2 by ESRI) utilizing
bathymetry layers and data was estimated as close as possible to sighting locations however
some data in the database was not defined in exact coordinates.
Student Involvement: The searching effort that I took part in was 75 hrs 32 min for 11 days
in June, July, and September of 2013. Trips ranged from 3 hrs to 11 hrs and 57 min
depending mostly on weather conditions. This does not reflect the extensive searching efforts
of Ocean Sounds and their database from 2007 to 2013. For this study I analyzed all of the
photographs to create a new Photo-ID database and re-sightings. I also analyzed all of the
sound recordings data and collected additional data from the field during the summer of
2013. I performed the statistical analysis, created graphs, maps, and writing.
Reading Boxplots: The median (divides the range in the middle with 50% of the data below)
is the thick middle line. The third quartile (75 percentile) is the top of the rectangle. The first
quartile (25 percentile) is the bottom of the rectangle. The thin “T” looking bars on the top
are the maximum and the thin “T” looking bars on the bottom are the minimum. Outliers are
the circles on the ends and the closely grouped outliers are the suspected outliers.
3
Abstract
The Atlantic White-sided Dolphin (Lagenorhynchus acutus) distribution is
understudied in Norway. Vessel based surveys were conducted in the Vestfjorden of northern
Norway and sightings occurred during 2005, 2007-2013. A total of 72 annual sightings were
observed including 55 Photo-ID individuals of which 29 individuals were re-sighted (2 of the
15 re-sighted individuals were observed on 6 occasions with gaps no greater than 2 years).
Sound recording were recorded using a hydrophone and the vocal behavior of clicks, buzzes,
whistles, and calls that were compared with activity; foraging, socializing, milling, and
traveling. Clicks were the most abundant sound produced and whistles were equally abundant
second to clicks. Stereotyped whistles were also observed (eg. 11-20 kHz, length 853 msec).
Calls were observed most common during traveling (32.4%) and least common during
foraging (18.8%). Buzzes varied (0-14.0%) and were absent during milling. Sound was
dependent on activity and sound production increased during socializing. Click production
increased in deeper water than shallower water, and was observed during foraging and
milling. Two different foraging strategies were observed; group cooperative herding of fish in
a shallower narrower fjord, Ingelsfjorden (8-10 m) and herding of fish by dolphin pairs in a
deeper wider fjord, Øyhellsundet (52-81 m) in northern Norway on two consecutive dates.
Frequent observations in this study of L. acutus may indicate a variety of population
behaviors and distributions however more research is required to identify and confirm them.
4
Introduction
Atlantic White-sided Dolphin Distribution and Biology
Atlantic White-sided Dolphins (Lagenorhynchus acutus) are part of the order Cetacea
(whales, dolphins, and porpoises), sub-order Odontoceti (toothed whales) in the Delphinidae
family and part of the a genus Lagenorhynchus of which half of the dolphins have northern
distribution; Atlantic White-sided Dolphins (Lagenorhynchus acutus), White-beaked
Dolphins (L. albirostris), and Pacific White-sided Dolphin (L. obliquidens) and the remaining
have southern distribution; Dusky Dolphin (L. obscurus), Peale's Dolphin (L. australis), and
the Hourglass Dolphin (L. cruciger). Atlantic White-sided Dolphins (further referred to as L.
acutus) are endemic to the North Atlantic cool (5-16⁰C) and low salinity water (Waring et al.
2008) along the continental shelf in 100-500m depths. They are distributed west from the
Davies straight to the Norwegian Sea east, and southward in North Carolina (35⁰ N) in the
west, in the Celtic Sea and perhaps the Azores (37-39 ⁰N) to the east (Reeves et al. 2002;
Figure 1). L. acutus are oceanic dolphins located near the continental shelf, slope, canyon
waters, and concentrate in areas of high seafloor relief, more densely in deeper areas (Reeves
et al. 2002) and sometimes near the coast (Cipriano 2009). The continental shelf edge can be
used as a navigation aid to travel or simply an area with high prey abundance (Stevick 2002).
L. acutus are also sighted year round in the deep waters north of Scotland and in the North
Sea in summer most likely following prey (Northridge et al. 1997). L. acutus tend to move to
northern latitudes during warmer months and closer to shore in the summer and offshore
during the winter (Reeves et al. 2002). Little is known about the northern limitations which
range at least the southern part of Greenland, southern Iceland, and the south coast of
Svalbard Island (Reeves et al. 1999). L. acutus are considered common in south-western
Norway although few sightings were reported (Northridge et al. 1997) and they sometimes
enter fjords and inlets (Reid et al. 2003).
5
Figure 1. Atlantic White-sided Dolphin (Lagenorhynchus acutus) distribution based on
Cipriano (2009, Figure 1 pg. 57). The “?” refers to areas of uncertainty in distribution.
Seasonal migration occurs in L. acutus when various types of prey are dominant at
different seasons (Cipriano 2009). Their prey consists of small schooling fish; Atlantic
Herring (Clupea harengus), Atlantic Mackerel (Scomber scombrus), Atlantic Cod (Gadus
morhua), Smelts (Osmeridae spp.), Sand Lances (Ammodytidae spp.), several types of squid
(Teuthida spp.; Reeves et al. 1999), Silver Hake (Merluccius bilinearis), Red Hake
(Urophycis chuss), and Cephalopods, mostly Long Fin Squid (Loligo pealeii) (Craddock et al.
2009). Sometimes they also follow their prey in their spawning migration of mackerel in
Ireland (Couperus, 1997). Seasonal prey and habitat variability occurs with different
alternating dominant prey of mackerel and mid-water fish (Cipriano 2002). L. acutus feed on
herring in Norwegian waters (Nøttestad et al. 2002) however L. acutus feeds mainly on
mackerel in Vestfjorden (Heike Vester personal communication). An abundance estimate for
6
L. acutus in the Atlantic Ocean estimate was reported over 100,000 dolphins (Hammond et
al. 2008); including 51,640 in the North American shoreline (Waring et al. 2006) and
including 96,000 west coast of Scotland (MacLeod 2004) and was reported data deficient in
eastern and central Atlantic (Cipriano 2009).
L. acutus males can grow up to 2.82 m and weight 230 kg, females can grow up to
2.43 m and weight 180 kg (Reeves et al. 2002). Females reach sexual maturity at the age of 6
to 12 years and males at the age of 7 to 11 years old (Cipriano 2009). Calving occurs between
June and July after 11 months of gestation and the calf is suckled for 18 months, females give
birth alternating years (Reeves et al. 2002). Calves are 120 cm long and weigh 25 kg (Perrin
and Reilly 1984). In the western Atlantic the mid-summer is the main calving time and a few
months longer in the eastern Atlantic (Weinrich et al. 2001). Some strandings of lactating
pregnant females suggest that some individuals may breed year round (Sergeant et al. 1980).
The L. acutus has a reported maximum life span of at least 22 years for males and 27 years
for females (Cipriano 2009). L. acutus has unique color patterns (Figure 2) that may be easily
identified and are suggested to be the most distinct species in their genus due to their unique
coloration (Mitchell 1970).
7
Figure 2. Photograph of an Atlantic White-sided Dolphin (Lagenorhynchus acutus) in
Vestfjorden, northern Norway 2013. Descriptive features labels with letters; (a) dark gray
dorsal side, (b) dark gray rostrum, (c) yellowish patch near the fluke, (d) white patches below
the dorsal fin, (e) light gray sides, (f) white ventral side, (g) black eye patch, and (h) white
lower rostrum. Photograph kindly provided by Heike Vester.
Social and Acoustic Behavior in Dolphins
Bottlenose Dolphins (Tursiops truncatus) are the model specie in the dolphin family
and the most studied cetacean. Dolphins live in fission-fusion groups that may alter by the
minute or hour (Conner et al. 2000, eg. Würsig and Würsig1977). A small primary group
consists of long-term associations (possibly kin) and a secondary large group meets together
8
to forage (searching for prey), socialize, or mate (Boness et al. 2002). The groups may be
separated by sex, age, kinship and reproductive status (Perrin & Reilly 1984). Pelagic
dolphins typically form larger groups (Norris and Dohl 1980) however group size may be
limited by the amount of prey in the school or single prey (Connor 2002). Behavior states are
based on activities and described as foraging (hunting), socializing, milling (resting), and
traveling (Shane 1990). Group foraging is more beneficial than solitary foraging, including
oceanic dolphins, and dolphins exhibit plasticity in foraging methods (Bowen et al. 2002).
The foraging methods are individually chosen by the dolphin and the preferred ones can be
transferred from mother to calf (Nowacek 2005). Bottlenose Dolphins push fish towards or
onshore and towards other groups of dolphins (Würsig 1986). L. acutus display similar
foraging strategies to the Dusky Dolphins (L. obscurus; Reeves et al. 1999) in Argentina that
hunt herds of fish to the surface, surrounding the fish working as a group, and taking turns
feeding on the fish (Würsig & Würsig 1979).
Dolphins communicate vocally and non-vocally through signals (Würsig et al. 1990).
They produce a variety of sounds; burst-pulse sounds, echolocation clicks and whistles
(Popper 1980). Burst-pulsed sounds are broadband discrete groups of clicks that have been
described as buzzes, calls, squawks, screams, and barks (Herzing 1996). Calls are between a
whistle and clicks and are referred to as pulsed calls. Pulsed calls are tonal signals with a
series of harmonics. Buzzes are repeated burst-pulse sequences at a highly repetitive rate
(Watkins 1967). Buzzes can be used in socializing and examining close objects. Echolocation
clicks are broad bandwidth sounds (30-40 kHz) and contain high frequencies (>100 kHz) and
are typically used for orientation, navigation, and prey detection. Whistles are continuous
narrow-band signals with harmonic frequencies and can be in the ultrasonic frequency range
(Lammers and Au 1996). Whistles are used for intraspecific communication (Herman and
Tavolga 1980). Frequency modulated whistles and burst-pulsed sounds are used for social
9
signals. A stereotyped whistle is a specific characteristic whistle repeated in several different
situations. Schevill and Watkins (1962, cited in Reeves et al. 1999) recorded L. acutus
"squeals" and a few clicks at 1-24 kHz. Steiner (1981) compared differences in five dolphin
species whistles in the North Atlantic (including the L. acutus) and described that L. acutus
produced pure tonal whistle dominant frequencies of 6-15 Hz (Nova Scotia, Canada and
Massachusetts, USA). Little is known about the vocal communication of L. acutus (Reeves et
al. 1999).
Atlantic White-sided Dolphin and White-beaked Dolphin Distribution
The White-beaked Dolphin (L. albirostris) has a more northern distribution and a
slightly less southern distribution than the L. acutus (Føyn et al. 2002, Table 1). Both dolphin
species have a similar latitudinal range that differs by water depth (Reid et al. 2003). Mixed
groups of L. acutus and L. albirostris have been observed in groups in the North Sea (Haase
1987). However L. acutus and the L. albirostris distribution overlap significantly and L.
acutus are more pelagic occurring in lower latitudes than the L. albirostris (Reeves et al.
2002). A shift in species occurred when the L. acutus became dominant and the L. albirostris
became scarce during reduction of herring and mackerel by fishing in the Gulf of Maine
(Kenney et al. 1996). The total abundance for both the L. acutus and L. albirostris in
Norwegian waters is 131,500 individuals (including 50,000 individuals in the Barents Sea)
(Føyn et al. 2002). The L. albirostris are the most common in the North Sea and a total of
both dolphin species combined was 20,000 individuals in the North Sea (Ottersen et al.
2010). Group size for both dolphin species was estimated to be 30 individuals (mostly sighted
with less) and sometimes found in large groups of several hundred dolphins, and in Norway
L. acutus and L. albirostris primary prey consists of herring, cod, and possibly capelin and
squid (Føyn et al. 2002).
10
Table 1. The distribution and occurrence of the Atlantic White-sided Dolphin
(Lagenorhynchus acutus) and White-beaked Dolphin (Lagenorhynchus albirostris).
Location
L. acutus
L. albirostris
Source
Norway, Iceland, Greenland, Canada,
common
common
Waring et al.
North-East United States, Ireland, and the
2009
United Kingdom
Faroe Islands
common
rare
Waring et al.
2009
Netherlands and Denmark (Kattegat/
rare
common
Baltic)
Waring et al.
2009
absent
common
Føyn et al. 2002
English Channel
absent
common
Føyn et al. 2002
Bear Island (near ice edge)
rare
common
Føyn et al. 2002
Northern Greenland, Greenland Sea,
Svalbard
Aim of Study
This study was the first reporting of L. acutus (a) vocal behavioral spectrograms and
descriptions of clicks, buzzes, calls, whistles, and stereotyped whistles, (b) relationship
between vocal communication and behavior, and (c) variability of foraging strategies
observed. In Norway this is the first reporting of a L. acutus Photo-ID study with reoccurring
identified individuals and distribution of L. acutus in Norway, specifically in the Vestfjorden
(northern Norway). The objectives of this study were to study (1) the distribution and
occurrence of the Atlantic White-sided Dolphins in Norway through sightings and Photo-ID,
(2) describe the vocal behavior; sound categories (clicks, buzzes, whistles, and calls), (3)
11
determine if sound production was dependent on activity (foraging, socializing, milling, and
traveling), depth (shallow and deep), and/or group affiliation, and (4) describe the presence or
absence of stereotyped whistles.
12
Methods
Study Area and Survey Platform
Photo-ID, behavioral notes, sounds (clicks, whistles, buzzes, and calls) from L. acutus
were collected in Norway from Vestfjorden (68.0500° N, 14.7667° E) during 2005, 20072013 (Figure 3). Daily L. acutus sighting research trips were conducted on an open rubber
Zodiac boat (7.3 m long with 250 HP outboard engine). Routes were determined based on
recent sightings, current sightings from other boats, listening underwater for L. acutus, and
areas not surveyed yet. A GPS track (Raymarine & GPS Widget for Android phones) of each
day’s entire trip was recorded with waypoint coordinates at the location of the first dolphin
sighted until the end of the encounter. Only the first location of a sighting was used in this
analysis in order to avoid recounting the same sighting although all locations were recorded.
Additional sightings were reported by Arctic Whale Tours and local media sources
[Norwegian Broadcasting Corporation (NRK), Aftenbladet, Lofotposten, Avisa Nordland
(AN), and Bladet Vesterålen]. Media sources were confirmed by visual inspection of
photographs to confirm the specie, unconfirmed dolphin species were classified as unknown.
13
Figure 3. Map of study area Vestfjorden (68.0500° N, 14.7667° E) in northern Norway. “X”
indicate the locations of the depth observations occurring in the shallow narrow straight
Øyhellsundet (52-81 m) and the deep wide area of Ingelsfjorden (8-10 m), Lofoten Norway.
Sightings and Photo-ID
6479 photographs (only good quality photos could be used for ID) of L. acutus were
collected and taken during 2007-2013. The photographs were taken by Heike Vester
Photographs were taken using a Canon EOS 1D Mark IV with a 100-400 mm zoom lens.
(additional photographs were collected from Arctic Whale Tours, Louise Normann Jensen,
Isabelle Dupre, Angelica and Maria Morell). The photographs were analyzed using the
methods of Photo-ID, identifying individuals based on natural markings (nicks, scars and
scratches) on the dorsal fins and the body of odontocetes following the protocol of Bigg et al.
(1982). Photo-ID was used to track individuals by date encountered and to enable identifying
14
re-sightings of individuals. Natural markings assist in long-term and reliable details to be
studied in the field over time in movement patterns, population size, dynamics, and social
structure. Subtle or small markings require maximum resolution to identify individuals. Some
natural markings are present at birth but many new natural markings will be added during
their lifetime (Whitehead et al. 2000).
Behavioral Sampling
L. acutus were observed underwater and surfacing from the boat. Behavioral notes
were written down on notebooks following methods of focal group sampling (recording the
behavior of all or most of the individuals in the group), continuous behavioral sampling and
event sampling (recording of all changes in the group behavior) (Altman 1974). Behavior was
categorized by the group’s activity; traveling, foraging, milling, and socializing (Shane 1990,
Table 2). All behavior was recorded with details on foraging methods in shallow and deep
water fjords.
Table 2. Description of dolphin behavior activities. Based on Henderson et al. (2012; Table 1
pg. 444) and behavior methods of Shane (1990).
Behavior
Description
Foraging
Variable movement of individuals and the group in a similar area that
visibly are chasing fish or rapid swimming (possibly jumps and dives).
Socializing
The group being close together (possibly touching) and active
movement behavior of jumps, tail slaps, and various movements of
individuals.
Milling
Resting with the group closely together slowly swimming and lacking
fast movements but staying close to the surface.
Traveling
Grouped together for slow, moderate, and fast speed. The group move
together in the same direction at a steady or rapid rate with surfacing
(possibly synchronized).
15
Acoustic Sampling
437 minutes of underwater sounds of L. acutus were recorded with hydrophones during
2008 and 2011-2013. Recordings of underwater sounds included clicks, whistles, buzzes, and
calls from L. acutus (only good quality sounds with less background noise could be used for
analysis). Two hydrophones [Reson TC 4032 Hydrophone (20 m cable) with a custom built
Etec amplifier and a Sound Devices 744T audio-recorder] were suspended on two parallel
sides of the boat. The depth of the hydrophone ranged 2-18 m depending on the depth of the
fjord.
This study investigated if the sounds produced were dependent on the context of
depth. The comparison of depth; shallow and deep were conducted on 22.07.2013 (shallow
data) & 23.07.2013 (both shallow & deep data) in the same shallow narrow straight
Øyhellsundet (52-81 m), Lofoten Norway and the deep wide area of Ingelsfjorden (8-10 m),
Lofoten Norway (Figure 3). The depth analysis considered the group to be the same both
dates and was re-sighted in the same location and identified using Photo-ID.
Analysis
Photographs were analyzed based on the quality and distinctive features of the
individuals. Photographs of poor quality were excluded from the database. The collected
photographs were enlarged on a PC monitor for detailed analysis using FastStone Image
Viewer 4.8 by FastStone. The best photograph of each L. acutus displaying identifiable
markings was magnified and named to be used as a primary identifiable photograph (Figure
4). The unidentified photographs were manually compared to the database for natural
markings to identify re-sighted individuals.
16
Figure 4. Example of Atlantic White-sided Dolphins (Lagenorhynchus acutus) Photo-ID
(22/07/2013) natural markings such as the large lower nick on the dorsal fin (indicated by a
red circle) and small top nicks (indicated by a red arrow). Norwegian Atlantic White-sided
Dolphin Photo-ID (Appendix 1).
A spectrogram is a visual representation of the frequencies of sound and amplitude which
consists of frequency (kHz) on the y axis and time (seconds) on the x axis. Spectrograms of
L. acutus whistles, call, clicks, and buzzes were created using Avisoft SAS Lab Pro 5.2.07
software by Avisoft Bioacoustics on a PC. Audio visual inspection was used to classify the
four types of sound categories; clicks, buzzes, calls, and whistles and each sound category
amount were counted per 10 seconds. Not all calls could be analyzed due to the background
noise mostly from boats. Only good quality sound files were used for analysis. The
recordings were analyzed using a sampling frequency of 48 kHz, resulting in 24 kHz
maximum spectrograms, ultrasonic sounds above 24 kHz were excluded. Stereotyped
whistles were identified visually using a spectrogram and an on-screen harmonic cursor (in
17
Avisoft SAS Lab Pro) to measure the frequency at the beginning, lowest point, highest point,
and inflection points and at the end of the whistle. Connections were investigated with
behavioral stages and the context of the water depth.
Organization of data and a histogram was created in Microsoft Excel with Windows 7.
Boxplot graphs were made using a statistical computer software “R” version 3.0.2 (The R
foundation for statically computing). Map bathymetry layers were acquired from a
geographic information system (GIS), ArcGIS for Desktop Advanced 10.2.2 by ESRI.
The sound recording data was changed manually from 10 second intervals to 1 minute
intervals and the remaining seconds at the end of the file were removed. The zeroes were
removed from the sound data set to extract more information from the data. Unfortunately it
is not possible to identify which individual produces which call. This impedes the statistical
analysis which requires independence of observation. Therefore it is not possible to tell if the
calls are produced by one or by different individuals. The limitation of statistics hinders the
depth of analysis.
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Results
Sightings and Photo-ID
A total of 72 L. acutus encounters were sighted during 2005, 2007-2013 in Norway
and were mostly concentrated within the vessel based survey study area of Vestfjorden in
northern Norway (Figure 4). Sightings varied by year with the highest amounts in 2011 (17
sightings), 2012 (17 sightings), and 2013 (18 sightings) (Figure 4). 10 sightings of Whitebeaked Dolphins (L. albirostris) during 2009-2014 in Norway and 6 unidentified dolphin
specie sightings during 2008-2010, 2012, and 2014 were recorded (Figure 5). More sightings
of L. acutus (Figure 4) were observed than L. albirostris (Figure 5) with few sightings of L.
albirostris within the study area (no sightings of L. albirostris were recorded during vessel
surveys in the Vestfjorden).
55 individual dolphins during 25 boat surveys dates (2007-2009 and 2011-2013) were
identified using the method of Photo-ID (Bigg et al. 1982) (Appendix 1). Identifications from
the Photo-ID resulted in 29 re-sightings (Table 3). The re-sightings were recorded per year; 2
in 2008 (# 3, 6), 1 in 2009 (#8), 8 in 2011 (#3, 6, 8, 9 three times, 10, 15), 2 in 2012 (# 3, 20),
and 12 in 2013 (# 1, 2 twice, 3 twice, 9 twice, 14 twice, 17 twice, 23) (Table 3). 2 dolphins (#
3 and 9) were re-sighted on 5 occasions, 6 dolphins (# 2, 8, 14, 17, 32) were re-sighted twice,
and 7 dolphins (# 1, 10, 15, 20, 23, 27, 38) were re-sighted once (Table 3). Sightings of # 3
occurred yearly during 2007-2008 and 2011- 2013 however # 9 sightings varied; once in
2008, three occurrences in 2011, and twice in 2013 (Table 3).
19
Figure 4. Sighting map of all Atlantic White-sided Dolphin (Lagenorhynchus acutus)
encounters observed during 2005, 2007-2013 in Norway. Sightings come from vessel surveys
and media sources. Each dot indicates a sighting and is coded by year observed. The dots do
not reflect the group size or individuals sighted.
20
Figure 5. Sighting map of White-beaked Dolphins (Lagenorhynchus albirostris) during 20092014 and unidentified dolphin specie sightings during 2008-2010, 2012, and 2014. All
sightings were based on media data with no observations of L. albirostris on the vessel
surveys. Each dot indicates a sighting and does not reflect the group size or individuals sited.
21
Table 3. Photo-ID re-sightings from 55 individuals from during 2007-2009 and 2011-2013
resulted in 29 re-sightings. Individual number refers to the Photo-ID database (Appendix 1)
of individuals identified by natural markings and is numbered based on the first sighting of an
individual with older sighting assigned with lower numbers.
Individual
First
Re-sighting(s) Dates
Number
Sighting
#
Date
1
10/06/2007
23/07/2013
2
10/06/2007
22/07/2013, 23/07/2013
3
10/06/2007
05/09/2008, 25/08/2011, 05/07/2012, 01/07/2013,09/08/2013
6
10/06/2007
05/09/2008, 29/07/2011
8
05/09/2008
11/08/2009, 19/06/2011
9
05/09/2008
25/06/2011, 29/07/2011, 02/08/2011, 22/07/2013, 23/07/2013
10
05/09/2008
24/06/2011
14
22/06/2009
22/07/2013, 23/07/2013
15
22/06/2009
19/06/2011
17
19/06/2011
22/07/2013, 23/07/2013
20
25/06/2011
11/01/2012
23
02/08/2011
22/07/2013
27
02/08/2011
22/07/2013
32
02/08/2011
05/07/2012, 09/08/2013
38
22/07/2013
23/07/2013
Sightings were evaluated based on month to test for seasonal occurrence (Figure 7).
The sightings were highest during summer months however this coincides with the main
search effort in the vessel surveys.
22
20
18
19
18
16
Number
14
12
10
10
8
5
6
4
3
3
2
2
2
5
3
1
1
0
Month
Figure 6. Encounters of Atlantic White-sided Dolphin (Lagenorhynchus acutus) by month
during 2005, 2007-2013 in Norway. Each sighting was counted as a single sighting and not as
an individual.
Behavioral Observations
L. acutus were observed on two occasions (22/07/2013 & 23/07/2013) displaying
variation in their foraging strategies. L. acutus were observed feeding on mackerel in a
narrow (0.2-0.3 nautical miles) and shallow (2.2-30 m, mainly concentrated in the 8-10 m
range) straight, Øyhellsundet (Lofoten, Norway) (Figure 6 a.). L. acutus moved as a group in
a large circular pattern chasing and rounding up fish. They pushed the fish towards the
shallower bays near land, this occurred within an estimated 0.5 km area. Visual behaviors
displayed during shallow water foraging included chasing fish, jumping, 180⁰ turns, and
underwater slaps (most likely from fluke). During this time the dolphins had no interest in the
boat and focused solely on foraging.
23
L. acutus were also observed feeding on mackerel in a different location on one
occasion in a wide (1.1-1.4 nautical miles) and deeper area (52-141 m, mainly concentrated
in the 52-81 m range), Ingelsfjorden on 23.07.2013 (Figure 6 b.). The foraging method
differed from the shallow observations; the group separated far apart into pairs and spread out
to the far end perimeters of the shores to scan for fish. They chased the fish and herded the
fish as a dolphin pair (instead as a group) and pushed the fish towards the shallow areas.
Visual behaviors displayed during deep water foraging included chasing fish and jumping.
The dolphins continued to express no interest in the boat and focused solely on foraging.
L. acutus were observed traveling between the shallow straight and the deeper area on
23/07/2013. During traveling on 23/07/2013 part of the group of 12 adults and 3 calves L.
acutus performed aerial displays of synchronized jumping; 2 pairs, 1 trio, and 2 quads were
observed. Unfortunately the sex was unable to be determined; some of the pairs appeared to
contain calves (possible mother-calf synchronization). L. acutus traveled at 10 knots with
occasional bow riding behavior observed. Upon arrival in the deeper area, the dolphins were
observed socializing and milling. Socializing consisted of the group approaching closer
together and aerial displays of jumps, rubbing or touching could not be determined. Milling
consisted of slow swimming and resting.
Acoustic Behavior
L. acutus produced clicks, buzzes, calls (Figure 7) and whistles (Figure 8). The rate of
clicks varied and spanned the entire frame of frequency range analyzed 1-24 kHz (Figure 7
a). The buzzes and calls observed were concave; frequency modulated with an instantaneous
frequency increasing with time in the beginning and ending with the instantaneous frequency
decreasing with time (Figure 7).
24
b.
Frequency (Hz)
a.
c.
Frequency (Hz)
Time (seconds)
Time (seconds)
Time (seconds)
Frequency (Hz)
Figure 7. Spectrogram of Atlantic White-sided Dolphin (Lagenorhynchus acutus) sounds
observed; (a) clicks, (b) buzzes, and (c) call.
25
Whistles & Stereotyped Whistles
898 whistles were recorded. A downsweep (a flat tone of higher frequency tone
changes to a falling tone of lower frequency) followed by an upsweep (the opposite of
downsweep) after the inflection point results in convex shaped whistles recorded. The
repeated whistle with the same pattern and close to or the same frequency contour is an
example of a stereotyped whistle observed (Figure 8). The beginning frequency of a whistle
was 19968 Hz and the end frequency was 16734 Hz (length 853 msec, highest frequency
19969 Hz and lowest frequency 10828 Hz) and the whistle has four parts with inflection
points (Figure 8). Many sterotyped whistled were observed in the data and repeated several
times in a row or repeated later in time.
Figure 8. Spectrogram of Atlantic White-sided Dolphin (Lagenorhynchus acutus) whistles.
The letters refer to the frequency measurements (Hz) of beginning, low, high, inflection
points and end frequency of the whistle contours; a. 19968 Hz, b. 18316 Hz, c. 15656 Hz, d.
26
13734 Hz, e. 12703 Hz, f. 13406 Hz, g. 11856, h. 10828 Hz, i. 12609 Hz, j. 15844 Hz,
k.17203 Hz and l. 16734 Hz. The second repeated whistles is an example of a sterotyped
whistle. An example of an echo and harmonic are labeled.
Hydrophone Recordings
The sound categories included; calls, whistles, buzzes, and clicks and the activities
included; milling, traveling, foraging, and socializing. 443 minutes from 8 recording dates
were used in the sound analysis of the L. acutus (Table 3). Each observation varied in activity
and group size. The main activity observed was foraging (233 min), milling (80 min),
socializing (77 min), and traveling (53 min); the group size ranged from 4 to 50 individuals
(Table 3). The group size was visually counted and estimated from the boat and photos taken.
Table 3. Overview of the 8 recording dates with group size and activities of Atlantic Whitesided Dolphin (Lagenorhynchus acutus). The activities are in minutes recorded.
Date
Group Size
Milling
Traveling
Foraging
Socializing
(sound/min) (sound/min) (sound/min) (sound/min)
19
0
0
29
10/08/2008
20-30
05/09/2008
4
0
0
48
0
02/08/2011
50
0
24
9
19
25/08/2011
10
9
0
7
0
05/07/2012
n/a
0
14
0
0
22/07/2013
20
0
0
92
0
23/07/2013
15
52
0
77
0
09/08/2013
40
0
15
0
29
80
53
233
77
Total
27
Sound Production and Activity
Clicks were the most abundant sound produced overall; during foraging/milling
(99%) and during socializing/traveling (98%) (Table 4). Whistles were the second most
observed sound; socializing (1.2 %), traveling (1.3%), foraging (0.55%), and milling
(0.61%), followed by calls; socializing (0.41%), traveling (0.63%), foraging (0.15%), and
milling (0.19%). Buzzes were the least observed sound and absent during milling. Every
activity resulted in a dominant presence of clicks followed by whistles, calls, and a low
amount of buzzes (Table 4).
Table 4. Total sounds in each category depending on the activity of Atlantic White-sided
Dolphin (Lagenorhynchus acutus).
Sounds
Calls
Percentage of
total sounds
Socializing
(sound/min)
123
0.41%
Traveling
(sound/min)
59
0.63%
Foraging
(sound/min)
102
0.15%
Milling
(sound/min)
18
0.19%
Whistles
Percentage of
total sounds
358
1.2%
119
1.3%
364
0.55%
57
0.61%
Buzzes
Percentage of
total sounds
29
0.096%
4
0.043%
76
0.11%
0
0%
Clicks
Percentage of
total sounds
29612
98%
9177
98%
66132
99%
9206
99%
Total Sounds
30122
9359
66674
9281
Due to the dominant presence of clicks, clicks were excluded for further analysis of
the remaining sound categories. Whistling was 65.4%-76.0% of the sounds produced and
whistling was approximately equally abundant during all four activity categories after
28
excluding the clicks, which dominated the sounds (Table 5). Calls were most common during
traveling (32.4%) and the least common during foraging (18.8%) (Table 5). Buzzes greatly
varied from 0-14% however the amount of buzzes was much less than the other sound
categories recorded and absent during milling. Every activity resulted in the abundance of
whistles followed by calls and buzzes (Table 5).
Table 5. The percentage of the sound categories (excluding clicks) during each activity of
Atlantic White-sided Dolphin (Lagenorhynchus acutus).
Sounds
Calls
Percentage of
total sounds
Socializing
(sound/min)
123
24.1%
Traveling
(sound/min)
59
32.4%
Foraging
(sound/min)
102
18.8%
Milling
(sound/min)
18
24.0%
Whistles
Percentage of
total sounds
358
70.2%
119
65.4%
364
67.2%
57
76.0%
Buzzes
Percentage of
total sounds
29
5.69%
4
2.20%
76
14.0%
0
0%
Total Sounds
510
182
542
75
An overview of all L. acutus sound categories occurrences were placed in histograms
(with zeros included) (Appendix 2). Further analysis excluded the zeros in the data to
investigate the presence of the sound categories observed. The total sounds (calls, whistles,
clicks and buzzes) of each activity (foraging, milling, socializing and traveling) were
compared (excluding zeros, Figure 9). The socializing medians vary, although there is a trend
that socializing produces more vocal behavior (Figure 9). The buzzes had too few data points
to determine a difference in the variables.
29
a.
c.
b.
d.
Figure 9. Total sounds of each category compared to activity of Atlantic White-sided Dolphin
(Lagenorhynchus acutus); (a) calls, (b) whistles, (c) clicks and (d) buzzes (zeroes removed in
figure). The x-axis is the activities and the y-axis is the amount of the respective sound
category.
30
Sound Production and Depth
In the depth analysis, the groups observed had estimated group sizes of 20 dolphins
(22/07/2013) and 15 dolphin (23/07/2013) individuals. On 22/07/2013, 11 dolphins were
identified using Photo-ID (including 7 re-sightings) and on 23/07/2013, 11 dolphins were
identified (including 6 re-sighted) (Appendix 1; Table 3). A total of 5 dolphins were resighted and present on both consecutive dates (Appendix 1). The groups were concluded to
be the same group of individuals based on the re-sightings, same location two consecutive
dates and the same observed shallow water foraging strategy both dates. A comparison of
depth and activity included two occasions of foraging observations in shallow waters and one
occasion of deep water foraging however milling was only observed in deep waters (Table 6).
Clicks were the dominant sound produced in both shallow and deep water (Table 6). More
clicks were observed per minute in deep foraging than shallow foraging when compared to
total recording time of each observation (Table 6).
The sounds categories were compared to depth resulting in a trend of more clicks
produced in deeper water than in shallow water (Figure 10c.). The medians were very close
for the call and whistle depth comparison therefore no difference could be determined (Figure
10). The buzzes had too few data points to determine a difference in the variables. Foraging
and milling were compared with depth, shallow milling was not observed during the depth
comparison dates (Figure 11). However there is a trend that more clicks are produced in deep
water than in shallow water (Figure 10c) and the trend is more clear during foraging and
milling (Figure 11c). Whistles are produced more during deeper foraging (Figure 11 b)
however there is no trend in overall whistles production and depth (Figure 10b). Buzzes were
not observed frequently.
31
Table 6. Depth comparison of activity and the sound categories of Atlantic White-sided
Dolphin (Lagenorhynchus acutus). Day 1 (22/07/2013) and day 2 (23/07/2013). Percentages
of sounds are in parentheses. Sound units are sounds per minute.
Activity
Day
Shallow
1
Recorded
(min)
88
Foraging
Shallow
2
32
Foraging
Deep
2
40
Foraging
Deep
2
Milling
31
Calls
Whistles
Buzzes
Clicks
Total
Sounds
15491
18
21
9
15443
(0.12%)
(0.14%)
(0.06%)
(99%)
0
45
2
5285
(0%)
(0.84%)
(0.04%)
(99%)
35
378
19
13065
(0.26%)
(2.8%)
(0.14%)
(97%)
15
61
4
8944
(0.17%)
(0.68%)
(0.04%)
(99%)
5332
13497
9024
Group Affiliation
Low variation was observed in the comparison of all sighting date groups and activity
(Appendices 3-6), however there is a trend that more clicks are produced during foraging
(Appendix 5c) which could be related to foraging depth. The buzzes had too few data points
to determine a difference in traveling and no buzzes were observed during milling (Appendix
6).
32
a.
c.
b.
d.
Figure 10. Sound categories compared to depth of Atlantic White-sided Dolphin
(Lagenorhynchus acutus); deep and shallow (sighting encounters from 22/07/2013 &
23/07/2013); (a) calls, (b) whistles, (c) clicks and (d) buzzes (zeroes removed in figure). The
x-axis is the depth and the y-axis is the amount of the respective sound category.
33
a.
b.
c.
d.
Figure 11. Foraging and milling compared to depth and the sound categories (sighting
encounters from 22/07/2013 & 23/07/2013) of Atlantic White-sided Dolphin
(Lagenorhynchus acutus); (a) calls, (b) whistles, (c) clicks and (d) buzzes (zeroes
removed in figure).The x-axis is the depth including activity and the y-axis is the
amount of the respective sound category. No shallow water foraging was observed on
the depth comparison dates.
34
Discussion
A total of 72 of Atlantic White-sided Dolphins (Lagenorhynchus acutus) were
observed during an eight year study (2005, 2007-2013) in northern Norway. Clicks were the
most abundant sound produced and had frequencies of at least 24 kHz. Whistles were equally
abundant after clicks and an example of a whistle had a frequency of 11-20 kHz. Calls were
observed most common during traveling and least common during foraging. Buzzes varied
and were absent during milling. Sound production increased during socializing. Click
production increased in deeper water than shallower water and was observed during foraging
and milling. Foraging was the most observed behavior during hydrophone recordings. Two
different foraging strategies were observed in the shallow (8-10 m range, group cooperation
of herding fish) and deep waters (52-81 m range, herding fish in dolphin pairs) on two
consecutive days.
Sightings and Photo-ID
72 total sightings of L. acutus (Figure 4) during 2005, 2007-2013 were observed. L.
acutus resulted in more sightings than L. albirostris. 10 sightings of White-beaked Dolphins
(L. albirostris) during 2009-2014 in Norway and 6 unidentified dolphin specie sightings
during 2008-2010, 2012, and 2014 were sighted (Figure 5). Most sightings of L. acutus
(Figure 4) were within the vessel survey area of northern Norway. In Norway this is the first
reporting of a L. acutus Photo-ID study with reoccurring identified individuals and
distribution of L. acutus in Norway, specifically in the Vestfjorden area (northern Norway).
55 individual dolphins during 25 boat surveys dates (2007-2009 and 2011-2013) were
identified using the method of Photo-ID (Bigg et al. 1982) (Appendix 1) and 29 re-sightings
that were also identified (Table 3). Creating a photographic database based on natural
markings enabled a tracking system for individuals sighted and individuals present during the
sound recordings and to be re-sighted. Most Photo-ID markings in this study were on the
35
dorsal fins in the form of nicks and scars. In the Gulf of Maine L. acutus has been identified
by scars and nicks on dorsal fins and unique pigment patterns (Weinrich et al. 2001). The
subtle markings and scraps on dolphins (Würsig and Würsig 1977) can be difficult to identify
and re-sight. Weinrich et al. (2001) studied the behavior and ecology of L. acutus in the New
England waters using Photo-Id and concluded that Photo-ID was a limited technique for this
specie due to the lack of distinctive markings and the difficulty of re-sighting them. However
no substantial pigmentations were observed in this study and in some cases dorsal fins can
remain constant over 12 years (eg bottlenose dolphins, Würsig and Harris 1990). Distinctive
markings can give rise to determining a home range (Caldwell 1955) therefore re-sightings
may indicate that L. acutus may have a home range (Wells et al. 1999) or possibly are part of
a resident population similar to the bottlenose dolphin (eg. Argentina, Würsig and Harris
1990), although further studies are needed to confirm this. However the sightings and resightings observed could be of residents and nonresidents that have overlapping ranges
(Rossbach and Herzing 1999) or based on prey migration (Selzer and Payne 1988).
Distribution in Norway
Separate populations of L. acutus has been debated. Palka et al. (1997) suggested that
three separate populations in the Western North Atlantic (Gulf of Maine, Gulf of St.
Lawrence, and the Labrador Sea) based on stranding, by-catch, and sightings however
Mikkelsen and Lund (1994) compared the skulls characteristics of 228 L. acutus and
concluded that there existed no separate populations based on phenotypic differences.
Recently Banguera-Hinestroza et al. (2014) suggested connectivity across the North Atlantic
across the Western and Eastern North Atlantic; these findings were based on nuclear and
mitochondrial genetics and agree with the Mikkelsen and Lund (1994) theory of no separate
populations of L. acutus.
36
L. acutus may also be underrepresented in stranding reports due to their offshore
distribution (Evans 1980). Strandings have risen in recent years and mass strandings have
been reported (Bogomolni et al. 2010). L. acutus has been greatly impacted through by-catch
(Reeves et al. 1999). Hunting still occurs in Canada, Greenland, and the Faroe Islands
(Hammond et al. 2008) which could affect the abundance. The Faroe Islands can take more
than 500 dolphins per year (Bloch and Mikkelsen 2009, cited in Banguera-Hinestroza et al.
2014) however the hunting impact on population is unknown (Banguera-Hinestroza et al.
2014).
L. acutus are described to have a pelagic distribution (Evans 1980) preferring cold (516⁰C) and low salinity water (Waring et al. 2008) with high bottom relief (100-500m) along
deep water canyons and troughs (Selzer and Payne 1988) however in this study L. acutus
were sighted near the coast (Cipriano 2009) close to shore and in various sized fjords (Reid et
al. 2003) in Norway. L. acutus are considered common in south-western Norway, south of
Norway (Northridge et al. 1997), west coast of Norway (Jonsgård and Nordli 1952), northern
Norway (Føyn et al. 2002) including sighted offshore in northern Norway (Nøttestad et al.
2002), and north up to Spitzbergen (77⁰N) (Øien 1996).
An indication of year round distribution may be present in Norway based on sightings
and Photo-ID (Figure 6) however this study conducted most of the vessel surveys in JuneSeptember, more year round data would need to be acquired to confirm. Sightings of
individual # 3 occurred yearly during 2007-2008 and 2011- 2013 (Table 3) although most
individuals were not sighted as frequently. L. acutus could be moving to northern latitudes
during warmer months and closer to shore in the summer (Reeves et al. 2002). Seasonal
distribution of L. acutus has been reported in New England, USA with more sightings
occurring in August to October than April to June (Weinrich et al. 2001) however in
Newfoundland, Canada the sightings were highest in July to October (Reeves et al. 1999).
37
Seasonal distribution of L. acutus occurs on the shelf waters from the Gulf of Maine to the
Middle Atlantic (Selzer and Paine 1988) and in the North Sea and northern Gulf of Maine
(Northridge 1997). The sighting distribution could be influenced by avoidance of survey
vessels (Wall et al. 2006) or avoidance of seismic activity (Stone, 2003). Seismic activity was
observed and recorded during the summer of 2013 in Vestfjorden. Lagenoryhnchus species
are exceptionally affected by seismic activity and display the most avoidance of all the
cetaceans altering their behavior to swim rapidly and as a result sightings are reduced during
air guns firing (Stone, 2003).
Foraging and Social Behavior
In the west North Atlantic L. acutus prey on sand lance near the continental shelf
(100-500 m) and in the east North Atlantic L. acutus prey on herring and mackerel (Weinrich
et al. 2001) including our observed feeding of mackerel in the Vestfjorden, Norway. The
foraging strategies varied greatly from the shallower (8-10 m range) narrow area in
Øyhellsundet, (northern Norway) and the deeper (52-81 m range) wide area in Ingelsfjorden
(northern Norway). L. acutus cooperate to herd and feed on schools of fish and are described
to use the same foraging strategies as the Dusky dolphins (L. obscurus, Reeves et al. 1999).
The shallower foraging strategy may be comparable to the Dusky Dolphin foraging strategy
in Argentina.
Würsig & Würsig (1979, 1980) described the dusky dolphin foraging in Argentina as
small groups of 6-15 animals herding anchovy to the surface and the dolphins swam closely
around and under the school of fish to herd them, taking turns swimming through the ball of
fish to feed and herded strays. Other surrounding dolphins up to 8 km have been observed
joining the foraging and reported aerial displays of jumping towards the dolphin foraging
group. Socializing occurs after foraging and Würsig & Würsig (1979, 1980) suggest it may
strengthen social bonds that are essential for foraging cooperation.
38
The deeper water foraging strategy was similar to the foraging strategies of bottlenose
dolphins, searching for prey in dolphin paired formations, up to hundreds of meters wide in
open waters, communicating and cooperating together (Norris and Dohl 1980) and chasing
fish into the shallows (Tayler & Saayman 1972). Weinrich et al. (2001) observed only a
single occurrence of L. acutus foraging in Stellwagen Bank (New England, USA, depth 1837m), part of the group 10-12 dolphins, (N= 35-50 dolphins) cooperated to herd sand lance
(Ammodytes spp.) into a ball and the dolphins alternated feeding. The ability to switch
foraging strategies to the environment is essential for survival. More possible foraging
strategies may be used that were not observed. This study is the first report of L. acutus
displaying flexibility in their foraging behavior (Bowen et al. 2002).
Behavioral observations during traveling included aerial displays of synchronized jumps
of 2 pairs, 1 trio, and 2 quads (included calves) L. acutus are highly acrobatic. Synchronous
movements are relationship based and displayed by mother and calf (Mann and Smuts 1999)
and male-male alliances that touch during surfacing and diving (Connor et al. 2000).
Unfortunately the sex could not be determined to indicate male-male or female-female pairs.
Socializing occurred with possible touching and solitary jumping. Therefore the indication of
alliances could be present in this population however further studies are needed to confirm.
Würsig & Würsig (1979, 1980) describes aerial jump displays of dusky dolphins as
communication, with distinctive splashes that most likely convey information about the
individuals or location. Dusky dolphins perform various aerial jumps; during foraging with
sharper and longer splash (possibly to frighten fish), towards other dolphin foraging groups,
and after foraging, that are more acrobatic with small splashes (Würsig & Würsig 1979,
1980).
Acoustic Behavior
Little is known about L. acutus acoustic behavior (Reeves et al. 1999). Echolocation
39
clicks are broad bandwidth sounds (30-40 kHz) and contain high frequencies (>100 kHz) and
are typically used for orientation, navigation, and prey detection. The interclick interval (rate
of clicks) changes in reference of the dolphin to its target (Au 1993).The rate of clicks varied
and spanned the entire frame of frequency range analyzed 1-24 kHz which contain ultrasonic
components (Figure 7 a). The frequency of the clicks in this study are consistent with
Schevill and Watkins (1962, cited in Reeves et al. 1999) which reported that L. acutus
produces clicks at 1-24 kHz. Dolphins produce short broadband clicks with frequencies up to
120 kHz in bottlenose dolphins (Au 1980) and up to 120 kHz with some maximum peaks of
250 kHz (ultrasonic) in L. albirostris (Rasmussen and Miller 2004). In this study the clicks
were however only analyzed up to 24 kHz; further analysis at higher frequencies should be
evaluated to test for click peak frequency which is unknown in L. acutus.
The buzzes and calls observed consisted of concave contours (Figure 7). Burst-pulsed
sounds such as calls and buzzes are not heavily studied (Lammers et al. 2004). High
repetition click trains and burst-pulsed echolocation sounds contain prey and social
information (Herzing 2004). Low frequency buzzing may occur during courtship, discipline,
play, aggression, and exploration (Herzing 1996).
Convex shaped whistles were recorded and described as downsweep, inflection point,
and upsweep contours (Figure 8). Steiner (1981) described L. acutus producing pure tonal
whistle dominant frequencies of 6-15 Hz in Nova Scotia and Massachusetts and compared
five different Atlantic dolphin species including L. acutus, bottlenose dolphins, long-finned
pilot whales (Globicephala melaena), Atlantic spotted dolphins (Stenella plagiodon), and
spinner dolphins (Stenella longirostris) whistles resulting in frequencies up to 20 kHz.
Steiner (1981) deduced that the differences in the whistles were greater in overlapping ranges
than in non-overlapping ranges of dolphin species. One selected convex shaped whistle had a
frequency of 11-20 kHz (Figure 8) which falls within the frequency range described by
Steiner (1981). L. albirostris whistles have been recorded with a larger range of frequency of
40
3-35 kHz with various whistle contours (Rasmussen and Miller 2004). Whistles are long
distance social signals used for communication and have localized frequency modulation
(Norris and Dohl 1980). Some of the whistles observed indicated stereotyped whistles (a
specific characteristic whistle repeated in several different situations).
Signature whistles are a learned unique whistle type that tells the identity of the owner
(Janik and Sayigh 2013, Caldwell 1990) and is copied in order to address another individual
(Janik and Slater 1998). Signature whistles in bottlenose dolphins aids in group cohesion
(Janik and Slater 1998) and individual identity (Sayigh et al. 1999). Additionally they are
observed when meeting other dolphins (Quick and Janik 2012), stress (Caldwell et al. 1990),
socializing (Quick and Janik 2008), when a dolphin is isolated (Caldwell et al. 1990), and
mother-calf reuniting (Smolker et al. 1993). Signature whistles have been suggested in L.
acutus (Steiner 1981) however this has not been studied and in order to recognize signature
whistles further extensive long term research is required including creating the first vocal
repertoire of L. acutus. This study was the first reporting of L. acutus vocal behavior
spectrograms and descriptions of clicks, buzzes, calls, whistles, and stereotyped whistles
(Figure 7, Figure 8).
Sound Production and Behavior
Sound production was compared with behavior to test for dependency on activity;
foraging, socializing, milling, and traveling (Shane 1990). Foraging was the most common
activity of the sound recorded dates, group size ranged from 4-50 dolphins (Table 3) although
overall sightings group size was 1-200 individuals (Figure 4). Echolocation clicks are
produced during foraging and consist of short pulses of high frequency and directionality to
detect prey (Zimmer 2011) and were the most abundant sound produced (Table 4). Social
signals such as whistles are used for communication and have localized frequency
modulation (Norris and Dohl 1980) and were equally abundant when clicks were excluded
41
(Table 5). Dolphins produce pulsed sounds below 5-10 kHz for communication (Caldwell
1967) and during foraging in bottlenose dolphins and Killer Whales (Orcinus orca, Marten et
al. 1988). However the calls were most common during traveling (32.4%) and the least
common during foraging (18.8%) (excluding the clicks, Table 5). Dolphin communication
signals are emitted in whistles or complex calls (Zimmer 2011). Buzzes varied in the
observations (0-14%) and were absent during milling when (excluding the clicks, Table 5).
Buzzes have been reported during foraging in wild bottlenose dolphins (Herzing 1996) and
foraging resulted in the highest amount of buzzes (14%) (clicks were excluded, Table 5).
Sound production increased during socializing in all sound categories (Figure 9). Whistles are
used for communication and produced more during foraging and socializing and less during
traveling or milling (eg. bottlenose dolphin, dos Santos 1990). However whistles were
produced similarly during all activities with the highest during milling (76.0%) and
socializing (70.2%, Table 5) most likely due to the low amount of milling observed.
Burst-pulse sounds are mainly produced during socializing (Schultz et al. 1995) and
foraging (dos Santos et al. 1990) in bottlenose dolphins however calls were produced most
during traveling (32.4%, Table 5). Buzzes are produced during foraging and playing in
bottlenose dolphins (Herzing 1996) and this agrees with our results of most buzzes during
foraging (14%) and socializing (5.69%, Table 5). Whistles are mainly produced during
traveling, milling, and socializing in Spinner Dolphins (Stenella longirostris, Norris et al.
1994). Whistle production occurred most during milling (76%) and socializing (70.2%)
however traveling (65.4%) and foraging (67.2%) whistles were similar (Table 5).
Echolocation clicks are the predominant sound produced during foraging (Herzing 2000) and
used for scanning prey in bottlenose dolphins (dos Santos et al. 1990) and the observations
agrees with the dominance of clicks produced (Table 4), however the percentage of clicks did
not greatly vary with activity (98%-99%, Table 4). This study was the first reporting of L.
acutus relationship between vocal communication and behavior.
42
Dolphins live in fission-fusion groups that may alter by the minute or hour (Conner et
al. 2000, eg. Wursig and Wursig1977) that are not maternally linked groups (Bigg et al.
1990) without group-specific dialects (Ford 1991), therefore dolphin groups should not
express group-specific dialects and should express low vocal variation between the groups.
The analysis of group affiliation resulted in low variation of sounds produced per sighting
group date when compared with activity (Appendices 3-6), this agrees with the fission-fusion
society (Conner et al. 2000) of dolphins lacking group-specific dialects (Ford 1991). A trend
was present with higher click production during foraging (Appendix 5c) however this trend
may relate to the depth, foraging strategy, or prey scanning effort.
Sound Production and Depth
Shallow water differs from deep water environments since shallow water consists of
more deflected sounds, echoes, and bottom absorption in relationship to the physical
environment (Katsnelson and Petnikov 2002). In shallower areas sound distorts
communication and is used in short distances or with very high frequency (Bradbury &
Vehrencamp, 1998). Sound production was compared with depth in two sand/mud bottom
fjords in northern Norway; the shallower fjord (8-10 m range), Øyhellsundet and the deeper
fjord (52-81 m range), Ingelsfjorden. More clicks were produced in deeper water than in
shallower water (Figure 10c) and during foraging (Figure 11c). Shallower water sound should
reflect back more sound than in the deeper areas and fish schools can greatly absorb and
scatter sound in shallow water (Makris et al. 2006). Therefore production of sound would
need to be altered in frequency or volume to accommodate and this agrees with the increase
of clicks observed. The sound categories were context dependent in shallower and deeper
water foraging clicks and greatly abundant in the deeper water (Figure 11). The variation in
the amount of clicks may be related to the depth and the foraging strategy used. Whistles
were produced more during deeper foraging (Figure 11 b) however there is no relationship in
43
overall whistles produced and depth (Figure 10b). Burst-pulsed sounds of calls and buzzes
were independent of depth and buzzes were rarely observed (Table 6). ).
Comparison of White-beaked Dolphins and Atlantic White-sided Dolphins
L. acutus are considered more pelagic than the L. albirostris (Evans 1980) and have
allopatric distributions (Waring et al. 2008). L. albirostris are considered more coastal in the
east North Atlantic (Evans 1992) and more pelagic in the west North Atlantic (Northridge
1997) and L. acutus was suggested to be the most abundant cetacean on the Atlantic Frontier
(Hardwood and Wilson 2001). The abundance for both L. acutus and L. albirostris in
Norwegian waters was estimated at 131,500 individuals (including 50,000 in the Barents Sea)
(Føyn et al. 2002). In Norway L. albirostris have been reported as more common of the two
species (Ottersen et al. 2010) however in this study L. acutus were sighted more frequently
than L. albirostris. The increase in frequency of sightings L. acutus and the decline of L.
albirostris in Norway could indicate a species shift or a normal occurring population that has
been understudied. A species shift was based on local climate interactions in Scotland with an
increase of common dolphins (Delphinus delphis) and a decrease in L. albirostris most likely
due to changes in sea temperature and specie temperature preference (MacLeod et al. 2005).
The possible shift in L. acutus and L. albirostris abundance could indicate a relationship to
temperature due to the close temperature preference of each specie with the division around
12⁰C (MacLeod et al. 2007). MacLeod et al. (2007) reported the distribution differences
based on habitat; L acutus preferring warmer deeper water and L. albirostris preferring colder
shelf waters in Scotland. However they suggested that habitat division may be more
dependent on prey than temperature. Prey preference has been suggested by Gaskin (1982)
that L. albirostris prefer benthic fish (cod, whiting and capelin) and L. acutus prefer nekton
fish (mackerel, herring and salmonids). In Vestfjorden, Norway L. acutus were observed
44
foraging on mackerel, L. albirostris was absent in sightings. Another shift in species has been
reported in the Gulf of Maine with an increasing presence of L. acutus and scarce L.
albirostris change due to reductions in fishing of herring and mackerel (Kenny et al. 1996)
however the abundance of fish has not become an issue in Norway.
Fewer sightings of L. albirostris may be hindered by the main search effort for L.
acutus however vessel surveys were opportunistic and an absence of L. albirostris still
resulted in Vestfjorden, Norway. L. albirostris could also be present outside the study areas
which were indicated in sightings reported by the media sources. Further studies are needed
to confirm the presence or absence of a species shift and sightings of L. albirostris in
Norway. However this study indicates a stronger presence of L. acutus and an indication of
an absence of L. albirostris in the Vestfjorden, Norway.
Conclusions
The coastal occurrence of L. acutus has not been well studied as the majority of
reports are pelagic based distributions. Many sightings of L. acutus including Photo-ID
individuals and re-sightings indicate a stronger presence of L. acutus than previous reported
in Norway. Vocal communication of L. acutus was tested and resulted in being dependent on
activity. Clicks were the most abundant sound produced and abundant during foraging.
Whistle production was the second abundant sound produced and more abundant during
milling and socializing. Sound production increased during socializing. Sound production of
clicks was dependent on depth and greatly abundant in deeper water more than in shallow
water. The flexibility of L. acutus foraging strategies in shallower and deeper waters was
observed. The known range of L. acutus includes the coast of Norway although the reduction
of sightings in the literature and the abundant counts are combination with L. albirostris
creates uncertainty in the abundance and distribution of L. acutus in Norway. A comparison
45
of L. acutus and L. albirostris resulted in a stronger presence of L. acutus observed in the
Vestfjorden area, northern Norway based on vessel surveys. Frequent observations in this
study of L. acutus may indicate a variety of population behaviors and distributions however
more research is required to identify and confirm them.
46
47
Acknowledgements
I’d like to greatly thank both of my supervisors Heike Vester and Jarle Tryti Nordeide for
their guidance in my master thesis. Thanks to both of you for creating this project and making
this all possible!
Jarle Tryti Nordeide, I am so grateful for his courageousness that expands past his main
research field to create and coordinate a project that interests me. He has incorporated marine
mammals into the master program expanding the options for all students. Thank you for your
teaching, knowledge, hard work and help with this project.
Heike Vester, I am so grateful for her ideas for the project and her essential past research
experience and data. Thank you for truly teaching me about marine mammals and sharing
your passion. I am so grateful for her dedication, teaching, hospitality, and hard work on this
project. Thank you for all of your support and inspiration to follow my dreams.
The FBA, thanks for all of your help in my education, funding this project, and all of the
wonderful professors and staff that have taught and helped me along the way. The University
of Nordland, thanks for the opportunity to change my career and facilitating my bachelor and
master degree.
The Lofotrådet, thanks for their stipend to make this project happen and for seeing the value
in local research and youth.
Thank you for contributing; Ocean Sounds, Felipe Matos, Arctic Whale Tours, Louise
Normann Jensen, Isabelle Dupre, Angelica and Maria Morell. Thanks to my family and
friends for your support and love. Norway, thanks for giving me the opportunity to continue
my education and explore a new part of the world that I now call home. Bjørn Hamran, thank
you for your motivation and believing in me.
48
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54
Appendix 1
Photo-ID of Norwegian Atlantic White-sided Dolphins
Photo-ID of Norwegian Atlantic White-sided Dolphin (Lagenorhynchus acutus). Labels: eg.
NAWSD-01-A-2007-06-10; NAWSD (Norwegian Atlantic White-sided Dolphins), 01
(Individual animal number), A [Group letter (date sighted for each group observed)], 200706-10 (date first sighted).
Name
Natural
Marking(s)
big middle
nick
First
Sighting
10/06/2007
Resighting(s)
23/07/2013
NAWSD-02-A-2007-06-10
no nicks,
scars on
dorsal
10/06/2007
22/07/2013
23/07/2013
NAWSD-03-A-2007-06-10
Plenty nicks
(2 low)
10/06/2007
05/09/2008
25/08/2011
05/07/2012
01/07/2013
09/08/2013
NAWSD-01-A-2007-06-10
55
NAWSD-04-A-2007-06-10
scars on back
10/06/2007
none
NAWSD-05-A-2007-06-10
Plenty nicks
(2 high)
10/06/2007
none
NAWSD-06-A-2007-06-10
low nick
(small)
10/06/2007
05/09/2008
29/07/2011
NAWSD-07-B-2008-08-10
high nick,
scar on front
of dorsal
10/08/2008
none
NAWSD-08-C-2008-09-05
plenty of nick 05/09/2008
(front top +
middle), scars
on dorsal +
back
11/08/2009
19/06/2011
56
NAWSD-09-C-2008-09-05
low nick, top
small nicks
05/09/2008
25/06/2011
29/07/2011
02/08/2011
22/07/2013
23/07/2013
NAWSD-10-C-2008-09-05
high nick
05/09/2008
24/06/2011
NAWSD-11-D-2009-06-22
plenty of
nicks (2 high
+ middle),
scars on
dorsal
22/06/2009
none
NAWSD-12-D-2009-06-22
top nick,
scars on
dorsal + back
22/06/2009
none
NAWSD-13-D-2009-06-22
plenty of nick
(2 high)
22/06/2009
none
57
NAWSD-14-D-2009-06-22
plenty of
nicks (2
middle)
22/06/2009
22/07/2013
23/07/2013
AWSD-15-D-2009-06-22
plenty of
nicks (high +
long + 2 low)
22/06/2009
19/06/2011
NAWSD-16-F-2011-06-19
plenty of
nicks (2 high
nicks)
19/06/2011
none
NAWSD-17-F-2011-06-19
high nick,
19/06/2011
scar right side
22/07/2013
23/07/2013
NAWSD-18-F-2011-06-19
plenty of
nicks (4 high
nicks)
none
19/06/2011
58
NAWSD-19-G-2011-06-24
plenty of
nicks (large
middle +
large low)
24/06/2011
none
NAWSD-20-H-2011-06-25
plenty of
nicks (2 high
+ low)
25/06/2011
11/01/2012
NAWSD-21-I-2011-07-29
scars on right
side
29/07/2011
none
NAWSD-22-J-2011-08-02
plenty of
nicks (2 high
+ low)
02/08/2011
none
NAWSD-23-J-2011-08-02
plenty of
nicks (high +
2 middle + 4
low)
02/08/2011
22/07/2013
59
NAWSD-24-J-2011-08-02
plenty of
nicks (high +
middle +
low)
02/08/2011
none
NAWSD-25-J-2011-08-02
plenty of
nicks (front
of dorsal + 2
high + 2
middle +
low), scar on
left yellow
stripe
02/08/2011
none
NAWSD-26-J-2011-08-02
plenty of
nicks (2 high
+ low)
02/08/2011
none
NAWSD-27-J-2011-08-02
plenty of
nicks (3 high)
02/08/2011
22/07/2013
NAWSD-28-J-2011-08-02
plenty of
nicks (high +
middle +
low)
02/08/2011
none
60
NAWSD-29-J-2011-08-02
bent dorsal
02/08/2011
none
NAWSD-30-J-2011-08-02
scars on left
side back +
left side dot
on yellow
stripe
02/08/2011
none
NAWSD-31-L-2012-01-11
scars on right
side
01/11/2012
none
NAWSD-32-M-2012-06-30
middle nick
30/06/2012
05/07/2012
09/08/2013
NAWSD-33-M-2012-06-30
big middle
nick
30/06/2012
none
61
NAWSD-34-N-2012-07-05
plenty of
nicks (2
middle + 2
low)
05/07/2012
none
NAWSD-35-N-2012-07-05
plenty of
nicks (3 high)
05/07/2012
none
NAWSD-36-N-2012-07-05
plenty of
nicks (2 high
+ 2 low)
05/07/2012
none
NAWSD-37-P-2013-07-16
plenty of
nicks (4 high)
16/07/2013
none
NAWSD-38-Q-2013-07-22
plenty of
nicks (2 top +
big middle +
2 low)
22/07/2013
23/07/2013
62
NAWSD-39-Q-2013-07-22
plenty of
nicks (high +
middle), calf
dorsal scars,
scar on head,
side
22/07/2013
none
NAWSD-40-Q-2013-07-22
calf middle
nick, scars on
left side
22/07/2013
none
NAWSD-41-Q-2013-07-22
plenty of
nicks (2 high)
22/07/2013
none
NAWSD-42-Q-2013-07-22
plenty of
nicks (high +
middle),
dorsal scar
22/07/2013
none
NAWSD-43-R-2013-07-23
calf high
nick, back
scar
23/07/2013
none
63
NAWSD-44-R-2013-07-23
plenty of
nicks (middle
+ low), scars
on right side
23/07/2013
none
NAWSD-45-R-2013-07-23
calf scar on
back
23/07/2013
none
NAWSD-46-R-2013-07-23
dorsal
23/07/2013
scratches
(base), 2 back
scars
none
NAWSD-47-R-2013-07-23
plenty of
nicks (high +
big middle +
2 low )
23/07/2013
none
NAWSD-48-S-2013-08-09
plenty of
nicks (4 high
+ 2 low)
09/08/2013
none
64
NAWSD-49-S-2013-08-09
right side scar 09/08/2013
none
NAWSD-50-S-2013-08-09
plenty of
nicks (top +
middle +
low)
09/08/2013
none
NAWSD-51-S-2013-08-09
plenty of
nicks (3 top +
2 big middle
+ 2 low)
09/08/2013
none
NAWSD-52-S-2013-08-09
plenty of
nicks (high +
big middle),
scars
09/08/2013
none
65
NAWSD-53-S-2013-08-09
plenty of
nicks (big
middle + 3
low )
09/08/2013
none
NAWSD-54-S-2013-08-09
plenty of
nicks (big
middle +
low)
09/08/2013
none
NAWSD-55-S-2013-08-09
plenty of
nicks (2 high
+ 2 low)
09/08/2013
none
66
Appendix 2
Histogram frequency distributions of sounds produced
Overall data histograms of sounds and the amount observed with zeros included.
a.
b.
c.
d.
Histogram frequency distributions of sounds produced in Atlantic White-sided Dolphin
(Lagenorhynchus acutus): (a) number of calls per minute observed, (b) number of whistles
per minute observed, (c) number of clicks per minute observed and (d) number of buzzes per
67
minute observed (zeros removed). The x-axis is the number of sounds in a one minute
interval for all observations. The y-axis is the frequency, or occurrence of sounds produced in
a one minute interval of all data. The numbers on top of the columns is the occurrence and
the vertical bar is the mean; (a) 0.6182 calls, (b) 3.990 whistles, (c) 271.8 clicks and (d)
0.5049 buzzes.
68
Appendix 3
Boxplots of sounds produced and socializing per sighting date
Boxplots of socializing sounds observed with the zeros removed.
a.
b.
c.
d.
Socializing sounds compared to all recording dates of Atlantic White-sided Dolphin
(Lagenorhynchus acutus); (a) calls, (b) whistles, (c) clicks and (d) buzzes (zeroes removed in
figure). The x-axis is the sighting dates of all recorded socializing observed and the y-axis is
the amount of the respective sound category.
69
Appendix 4
Boxplots of sounds produced and traveling per sighting date
Boxplots of traveling sounds observed with the zeros removed.
a.
b.
d.
c.
Traveling sounds compared to all recording dates of Atlantic White-sided Dolphin
(Lagenorhynchus acutus);(a) calls, (b) whistles, (c) clicks and (d) buzzes (zeroes removed in
figure). The x-axis is the sighting dates of all recorded traveling observed and the y-axis is
the amount of the respective sound category.
70
Appendix 5
Boxplots of sounds produced and foraging per sighting date
Boxplots of foraging sounds observed with the zeros removed.
a.
c.
b.
d.
Foraging sounds compared to all recording dates of Atlantic White-sided Dolphin
(Lagenorhynchus acutus); (a) calls, (b) whistles, (c) clicks and (d) buzzes (zeroes removed in
figure). The x-axis is the sighting dates of all recorded foraging observed and the y-axis is the
amount of the respective sound category.
71
Appendix 6
Boxplots of sounds produced and milling per sighting date
Boxplots of milling sounds observed with the zeros removed.
a.
b.
c.
Milling sounds compared to all recording dates of Atlantic White-sided Dolphin
(Lagenorhynchus acutus); (a) calls, (b) whistles, (c) clicks (zeroes removed in figure). The xaxis is the sighting dates of all recorded milling observed and the y-axis is the amount of the
respective sound category. No buzzes were observed.
72